Photosensitive material and a process of making same



United States Patent PHOTOSENSITIVE MATERIAL AND A PROCESS OF MAKINGSAME Theodor Haefeii, Ennethurgen, Switzerland, assignor to CinetechnikA.G., Zurich, Switzerland No Drawing. Application March 15, 1955 SerialNo. 494,547

Claims priority, application Germany March 15, 1954 5 Claims. (Cl.96-75) This invention relates to photosensitive material and moreparticularly to light sensitive photographic material containing diazoand tetrazo compounds of the diphenylamine group as light sensitivecompound, and to a process of making same.

Diazo compounds of bases of the diphenylamine series stabilized by meansof aluminium or magnesium salts, and their coupling or, developing with2,3-hydroxy naphthoic acid arylides and other coupling components of thenaphthol AS group are known. It is furthermore known that said diazo andtetrazo salts of bases of the diphenylamine series are unstable inaqueous solution, for instance, in the dyeing bath, and on carriers.Such compositions, in the undeveloped state, can be stored, at the most,for 2-3 days only.

It is one object of the present invention to provide a photographiclight sensitive material comprising diazo and tetrazo salts of thediphenylamine series which compounds are stable for a considerableperiod of time and, therefore, are useful in the manufacture ofphotographic and movie fihns, of photographic papers and otherphotographic materials.

Another object of the present invention is to provide a process ofmaking such light sensitive photographic material and of substantiallyincreasing the sensitivity to light of such material.

Other objects of the present invention and advantageous features thereofwill become apparent as the description proceeds.

According to the present invention, it was found that treatment of acellulose hydrate layer with aqueous solutions of diazo and tetrazosalts derived from diphenylamine bases yields a light sensitive materialwhich is stable and can be stored for an almost unlimited period oftime. By subjecting such a photosensitive layer to a ripening processfor 2-3 months at a temperature of 18-22 C. preferably 20 C. whileexcluding light and air, the sensitivity of said material whichinitially has a sensitivity of about 11 pictures per second can beincreased to such an extent that it is possible to use said material,for instance, in a film printing machine with a speed of 30-40 picturesper second.

Said ripening process furthermore imparts to the light sensitive layermore uniform gradation than is exhibited by such layer directly afterapplying said diazo and tetrazo salts to the cellulose hydrate layer.Such a more uniform gradation, of course, is of great advantage in theproduction of satisfactory photographic pictures. The optimum gradationbeing obtained after a ripening period of about 14 days. The higher theinitial gradation the lesser its reduction on ripening. When startingwith initial gradations of 1.5, 2 and 3 these are reduced to 0.8, 1.6and 2.4 respectively.

The sensitivity to light of said diazo and tetrazo salts can be furtherimproved by using said salts in their 2,893,866 Patented July 7, 1959purest form, i.e., without any addition of filler salts as they werepresent in the diazo compounds heretofore known in the dyestulfindustry.

Gradation of the finished color picture can readily be affected andadjusted and can be considerably varied from soft to hard, i.e., fromsemitone for lavender prints to high contrasts for outline drawings.According to the present invention, gradation depends to a considerableextent upon the size of the dyestuif molecules. Thereby the molecularsize is to be understood as particle size. Optimum gradation is achievedwith compounds of the smallest molecular size. This is probably due tothe fact that larger particles tend to form colloidal particles insolution.

Due to the fact that the salts used in accordance with the presentinvention are salts e.g. chlorides or sulphates of diazonium compounds,which in an aqueous medium form true molecular solutions, which obey tothe laws of electrolytic dissociation, the development of the particlesize is in close relationship to azeocomponents used in the couplingreaction (e.g. derivatives of beta-hydroxynaphthoic acid) which in turnform colloidal solutions in aqueous media. The effect of these naphtholsof the AS series on the molecular size of the dye to be formed bycoupling varies Within wide limits, so that the ability of gradation ofthe light sensitive material may be Widely varied by choosing theappropriate coupling component and by control of the pH-value during thecoupling-reaction which is penformed in aqueous solution. Thereby theoptimal gradation (for movie and photographic films) is obtained withcompounds (coupling-compo nents) which due to their chemicalconfiguration form smallest dye particles. The pH-value of the couplingcomponent (azo component in aqueous solution) is between about 12 and13.5, the temperature of the solution between 18 C. and 22 C.

The diazo and tetrazo compounds of the diphenylamine series are chargedin aqueous solution with such a strongly positively polar-charge thatthe strongly negatively polar cellulose hydrate surface as it isobtained, for instance, on superficially saponifying acetyl cellulose bymeans of alkali hydroxide, binds so many dyestuff molecules thatsatisfactory depth of color is combined with sufiicient gradation and isachieved even on sensitizing said cellulose hydrate foil only on oneside.

It is very surprising that diazo and tetrazo salts of the Idiphenylamine series can be employed for making photographic lightsensitive materials, since it was known that said salts are unstable inaqueous solution. Their combination with a cellulose hydrate carrier issurprisingly stable. A further increase in stability is achieved byadding acetic acid to the dye bath. The pH-value of the layer should,however, not exceed 7. Any other suitable aliphatic carboxylic acid likecitric acid or tartaric acid may also be used.

The diazo and tetrazo salts of the diphenylamine series are suitable notonly for producing so-called black-andwhite pictures but also forproducing colored pictures.

The following examples serve to illustrate the present inventionwithout, however, limiting the same thereto.

Example 1 An acetyl cellulose film is superficially saponified by atreatment with 5% sodium hydroxide solution at a temperature of 65 C.during 12-18 minutes and is thereby partly reconverted into cellulosehydrate on its surface. Said alkaline bath contains 60 ml. of a suitableleveling agent per liter, preferably an addition product of ethyleneoxide to alkyl phenols having 12-14 carbon atoms 2;sas,see s as theiralkyl chain. Such addition compounds correspond, in general, to theformula wherein Ris an alkyl radical having from 12-14 C-atoms and. naninteger from 3-19,.preferably 11-13. Thepreferred thickness of thehydrolised layer being about 0.01 mm., but may vary between 0006-0012.

An. aqueous solution of the. tetrazo. compound of p aminodiphenylamino-pazo-4-amino 5-ethoxy-2-toluene instabilizedform, said. solutioncontaining 100' goof said dyestufi per literwbath, isappliedtosaidsuperficiallysaponified acetyl celluloseby means of rubberrollers. The dye bathtcontains. preferably 10 cc. of acetic acid perliter in order to stabilize the resulting light sensitive blank filmmaterial for anunlimitedperiod oftime when keeping-said. material underexclusion fromlight-and air, for instance, in tin cans. Before storingthesensitized film isedried at 30-45 C. preferably 40 C. in anair-stream under exclusion of ultra-violet radiation.

Developing. the exposed film by means of the anilide of -2.3-hydroxynaphthoic acid yields a black-and-white photographic picture.

Example 2 Example 3 An. aqueous solution of the stabilized diazocompound of 4t-amino diphenylaminesulfateon chloride which contains 20cc. of acetic acid and 100 g. of said diazo compound perlitenis appliedto superficiallysaponified cellulose acetate foil, asdescribedinExample. 1.

Exposure to light of said photographic material, and development with adi-acetoac etic adid-o-tolidide yields a photographic pictureinyellow-and-white.

Example 4 An aqueous solution of the stabliized diazo compound of4-amino 3-methoxy diphenylamine which contains 12 cc. of acetic, acidand 100 g. of said diazo compound per liter, is appliedtto asuperficially saponifiedcellulose acee tate'foil, as described inExample 1.

Exposure to light of said photosensitive material and development with2,5 dimethoxy 4 chloro anilide of 2.3-hydroxy naphthoic acid yieldsaphotographic picture inred-and-white.

Example 5 A cellulose hydrate-film prepared asin- Example 1 is treatedwith a solution containing 100 gms. of the diazo compound of4-amino-4rethoxydiphenylamine in one liter-of water containing 16 mlacetic acid. After exposure under a pattern and development with2.3-hydroxyanthracene carboxylie acid-ortho-toluidide a green picture isobtained.

1 Example 6 A11- acetyl cellulose film treated according to one of theforegoing Examples 1-5 with a diazo compound after exposure is treatedat a temperature of '20 C. with an aqueous solution of the couplingcomponent 2.3-hydroxy-.

naphthoic. acid-ortho-toluidider The pictures. obtained are. sharnandclear becausethe size of the naphthol molecules corresponds to that ofthe diazo component.-

When working at higher temperatures the naphthol molecule becomes largerand therefore, the particle size of the dye becomes also larger.

Example 7 An acetyl cellulose filmpretreated according to one of theforegoing Examples 1-5 with a diazo compound, after exposure istreated-with an aqueous solution of the coupling component2,-3-hydroxynaphthoic acid-orthoanisidide at any desired temperature.The particle size of the dye will in any casebe larger than in Example6, the chemical structure of this coupling component being such that itcan-be adapted to the molecule of the-diazonium salt neither by choiceof the temperature nor by controlling the pH value.

Example 8 The acetyl cellulosefilm pretreated with a diazo-compoundasdescribed in any of the Examples, 1-5, after, exposure is treated withan aqueous solution of'the coupling component2-acetosacetlyaminor6-ethoxybenzothiazoleat any-desired temperature. IIn: any case, dueto the molecular structure of the azo component, the.particle size of thev dyeformed will be larger than; inExample 8. Even.the control of the .pH-value will notadapt-the molecule ofthis component.to the molecule of thediazonium compound.

In place of the above mentioned diazo andtetrazocompounds, there canbeused other diazo and tetrazo compounds of basesof the diphenylamineseries, which are known in the art.

The most preferred diazo compounds to be used in the process of thisinvention are 4-aminodiphenylamine and its substitution products havingat least one lower alkyl or lower alkoxy group in one of the phenylrings of said amino diphenylamine amino compound. The tretrazo compoundsused in this inventionare derived from-p,p'-diphenylamine and itssubst'itution'productsas. indicated. above; Especially suitablecompounds are apparently compounds obtained. byncoupling diazotized4:amino..dia phenylamine with iaromatic amino compounds, such as, 7lower; allroxy substituted. tolidine compoundsand the like Stabilizationof said compounds is effected, for instance, by the addition ofalurniniumsulphate-or-magnesiumsul p phate. Stabilization mayalso beeffected by removing the oxidation-products from .the diazo compoundsand, precipitating the latter-with neutral salts which do. not. undergohydrolytic cleavage at room temperature ,inthe p s qe f a dhav n a-s lpH- u ,.,l lre bor acid. Anad dition of materials which, like ureabindthe free nitrous acid is favourable.

Satsistactory results are obtained when using about 10%- solutions ofsaid dyestuifcomponents. It is, of course, also possible to employsolutions of alower concentration. The-concentration should, however,not. exceed about 10%= and should not be substantially lower than-6%.:

After. applying the solutionof said diazo and tetrazo. compounds-s tothe .cellulose hydrate .base, the material is subjected to adryipggprocess at-a temperature between. 9-1451 nipreferah y 40f C.

As,statedabove thqnew photosensitive material haste sensitivity whichpermits exposures of of a second and even less, i.e. of a second.

In place of superficially saponified acetyl cellulose, there may be usedother types of regenerated cellulose or cellulose hydrate for microfilms, whereas a cellulose hydrate derived from acetyl cellulose hasproved to be the preferred starting material for movie films.Superficial saponification of said cellulose acetate material may becarried out with sodium or potassium hydroxide solutions of aconcentration between about 2% and about 5%. The temperature ispreferably between about 62 C. and 68 C. In place of the leveling agentadded to the alkali hydroxide solution of Example 1, there may be usedother leveling and emulsifying agents such as wetting agents known inthe art, for example Turkey red oil, alcohols, etc.

In place of acetic acid, there may be added other organic acids to theaqueous solution of diazo and tetrazo salts of bases of thediphenylamine series such as the aliphatic carboxylic acids having 1-4carbon atoms, provided that the pH does not exceed 7. Apparently it isof advantage to said solution to impart a pH of between about 5 andabout 7.

Ripening of the new photosensitive material and increase of itssensitivity to light is elfected by simply storing the said materialwhile excluding excess of air and light at a preferred temperature of 20C. maximum light sensitivity and gradation being achieved within 3-4months and 2 Weeks respectively.

Of course, many changes and variations may be made in the preparation ofthe cellulose hydrate layer, the preparation of the diazo and tetrazocompounds employed, the method of applying said diazo and tetrazocompounds to said cellulose hydrate layers, the ways and means ofincreasing the sensitivity to light and the stability as well as thegradation properties of the new photosensitive material, and the likemay be made by those skilled in the art in accordance with theprinciples set forth herein and in the claims annexed hereto.

The term cellulose hydrate as used herein and the claims annexed heretoindicates any regenerated cellulose which is obtained by alkalinesaponification of cellulose esters. The preparation of the carrier usedin this invention is more fully disclosed in my copending applicationSer.No. 408,037.

I claim:

1. A process of making light sensitive cinematographic and photographicmaterial, said process comprising in combination, the steps of embeddingthe light sensitive substance consisting of a chloride of nitroso-freediazo compound of 4-methoxy-4-amino-diphenylamine having the formula ina superfically saponified cellulose hydrate layer, said layer havingbeen saponified by caustic sodawith an equalizing agent having theformula wherein R is an alkyl radical having from 12-14 C-atoms and 11an integer from 3-19, and ripening the embedded diazo compound bystorage during a period of one to three months, whereby film of constantlow contrast characteristics is produced.

2. The process in accordance with claim 1, comprising the initial stepof adding to the diazo compound prior to its application to thecellulose hydrate layer from 10 to 25 cm. CH COOH per liter of solution.

3. The process in accordance with claim 1, wherein the cellulose hydratelayer is formed by superficially saponifying an acetyl cellulose foilwith a 5 to 10% NaOH solution containing an equalizing agent having theformula at a temperature of 62 C. to 68 C., wherein R is an alkylradical having from 12-14 carbon atoms and n is an integer from 3-19,the chloride of nitroso-free diazo compound of4-methoxy-4-aminodiphenylamine being strongly positively charged.

4. The product of claim 1.

5. The process in accordance with claim 1, comprising charging the diazocompound with a strongly positive polar charge to provide a stronglynegatively polar cellulose hydrate surface, whereby the ripening isfacilitated.

References Cited in the file of this patent UNITED STATES PATENTS2,789,904 Benbrook et al. Apr. 23, 1957 FOREIGN PATENTS 337,868 GreatBritain Nov. 13, 1930

1. A PROCESS OF MAKING LIGHT SENSITIVE CINEMATORGRAPHIC AND PHOTOGRAPHICMATERIAL, SAID PROCESS COMPRISING IN COMBINATION, THE STEPS OF EMBEDDINGTHE LIGHT SENSITIVE SUBSTANCE CONSISTING OF A CHLORIDE OF NITROSO-FREEDIAZO COMPOUND OF 4''-METHOXY-4-AMINO-DIPHENYLAMINE HAVING THE FORMULA